Well completion method



July 23, 1968 R. J. GOODWIN 3,393,736

I l WELL CCMPLETION METHOD l Filed Aug.. 17, 196e United States Patent O 3,393,736 WELL COMPLETION METHOD Robert J. Goodwin, Oakmont, Pa., assignor to'Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware f Filed Aug. 17, 1966, Ser. No. 573,080 9 Claims. (Cl. 166-12) ABSTRACT F THE DISCLOSURE A method of completing a well having casing set through an incompetent fluid-bearing formation in which openings are cut in the casing, a cavity having a width substantially larger than the width of the opening in the casing is cut in the incompetent formation by means of van abrasive-laden fluid, and thereafter the cavity is filled with solid particles which are bonded together to form a permeable coherent mass.

This invention relates to a method of completing a well, and more particularly to the prevention of ow of sand into a well having casing set through an incompetent, fluid-bearing formation.

Many underground formations containing valuable fluids, such as oil or natural gas, are referred to as incompetent formations because they are unconsolidated or so weakly consolidated that the pressure drop at the unsupported, exposed face of the formation resulting from the flow of formation fluids toward the well exceeds the strength of the formation and causes particles of the formation to break loose and ow into the well. The flow of sand into the well may plug the well and make necessary frequent work over of the well to maintain production. If the underground formation is under high pressure, the sand from the formation may travel through well equipment at high velocities and cause severe erosion of the well equipment.

One method that has been widely used to prevent sanding of wells penetrating incompetent formations is to pack gravel between the face of the formation and a slotted liner set in the well. The gravel supports the formation and obstructs flow of sand to the well. The liner prevents ow of the gravel into the well. An important objection to the use of gravel packs and liners to prevent flow of sand into a well is the high cost of the liner and the packer required to seal the space between the upper end of the liner and the casing. Moreover, it is difficult to fill completely the space behind the liner. Sand can then shift to plug the gravel pack and thereby reduce the wells productivity.

It is desirable after a well has been drilled to its total depth to set casing through the potentially productive formations. The casing is cemented in place by displacing a slurry of cement downwardly through the casing, around the lower end of the casing, and upwardly through the annulus between the casing and the borehole wall. The casing and its surrounding cement sheath isolate the productive formations from other formations penetrated by the well and, in the case of incompetent formations, provide support for the incompetent formation immediately adjacent the well. The casing is perforated through the potentially productive formation to vallow flow from the formation into the well, The usual method of perforating the casing is by means of shaped charges of explosives which form slender holes extending from the casing a short distance outwardly into the formation. The holes taper to a point at their outer end.

This invention resides in a method of completing a well penetrating an incompetent, fluid-bearing formation 3,393,736 Patented July 23, 1968 ICC in which casing is cemented in the formation to control `movement of sand from the formation into the Well. An opening is cut in the casing and adjacent formation by means of a high-velocity stream of a uid containing entrained abrasive particles to form a cavity having a width near its outer end substantially larger than the diameter of the opening in the casing. A granular material is displaced through the openings in the casing into the cavity cut by the abrasive stream, and particles of the granular material are cemented together to form `a unitary permeable mass expanding outwardly from the outer surface of the casing.

In the drawings:

FIGURE l is a vertical sectional view of a portion of a well penetrating an incompetent formation showing nozzles supported in the well while openings are cut in the casing and cavities are cut in the surrounding formation.

FIGURE 2 is a vertical sectional view of the well illustrated in FIGURE 1 after the cavities in the incompetent formation have been cut to the desired size and solid particles have been displaced into the cavities to form a unitary mass supporting the exposed face of the incompetent formation.

Referring to FIGURE l, the lower end of a well indicated generally by reference numeral 10 is shown with casing 12 extending through an incompetent, fluid-bearing formation 14 to a total depth 16. Casing 12 is cemented in place in the usual manner by displacement of cement downwardly through the casing and upwardly through the annulus between the casing and the borehole wall to form a cement sheath 18 surrounding the casing 12.

In the completion of the well by this invention, perforations 20 are cut through the casing 12 and cement sheath 18, and enlarged cavities 22 are cut in the formation adjacent the perforations 20 by means of a highvelocity stream of a fluid containing entrained abrasive particles. Preferably, a slurry of abrasive particles in a liquid is used and the cutting medium will hereafter be referred to as a slurry. The slurray is pumped down the well through tubing 24 and is discharged through nozzles mounted in a suitable nozzle head 26 to erode holes through the casing and surrounding cement sheath. The abrasive slurry discharged from nozzle head 26 is directed outwardly in a thin, high-velocity stream to cut a cavity 22 in the surrounding formation. The slurry is diverted at the outer end of the cavity and returns through the perforations 20 to the borehole of the well. The return ow of the slurry to the perofrations 20 enlarges the cavity to a width substantially larger than the perforations 20 and erodes cement from the casing adjacent the perforations. The slurry of liquid then flows upwardly through the annulus and is discharged from the well at the surface. To obtain the desired enlargement of the cavity, flow back into the Well is essential; hence, space must be provided between the nozzle and the casing to allow the backllow.

FIGURE 1 of the drawings shows a well with two perforations 20 and cavities 22. Other perforations and cavities `can be cut at intervals throughout the incompetent oilbearing formation 14 to provide any ldesired number of openings in the casing. In a preferred method of this invention, a single notch extending for the full circumference of the casing and a circular cavity extending outwardly into the formation from the notch is cut by rotating in a horizontal plane the nozzle head from w-hich the abrasive slurry is discharged. Suitable apparatus for cutting the notch in the casing and the surrounding -cavity is illustrated in U.S. Patent No. 3,254,720 of I. L. Huitt et al.

An abrasive slurry is discharged from the nozzles until cavities 22 of a desired size are formed as illustrated in FIGURE 2 of the drawings. After the cavities are cut, the tubing 24 and nozzle head 26 are withdrawn from the well. A slurry of solid particles 28 suspended in a liquid is pumped down the well and into the cavities 22. The liquid lters outwardly through the surrounding formation 14 and deposits the particles in the cavity 22. Pumping of the slurry of liquid and solid particles is continued until the particles ll the cavities 22. Another method of placing the gravel is to close the annulus surrounding tubing 24 and displace a slurry of gravel through the tubing 24 and nozzle head 26 and into the cavities 22. Ordinarily, an increase in t-he pressure on the liquid at a constant pumping rate will indicate when the cavities have .been filled. Filling the cavities with gravel can also be accomplished by pumping a slurry containing a measured volume of gravel adequate to fill the Icavities down the well and into the cavities at a slow rate to avoid parting the formation.

The particles 2S are bonded together to form a substantially unitary permeable mass completely lling the cavities 22 and thereby providing support for the exposed faces of the incompetent formation 14 forming the walls of the cavities 22. In a preferred method of bonding t-he particles 28 together, the particles are provided with a coating of a resin-forming liquid or semiliquid material capable of setting into a resin which is insoluble in water and oil before they are suspended in a liquid and pumped down the well. The coating on the particles may contain sufficient catalyst to cause the coating to set to a hard, strong resin at the conditions of temperature and pressure existing in the formation 14 or may be 0f a material that will set to form the desired strong bon-d without a catalyst. Another method of bonding the particles together to form the desired strong unitary mass is to coat the particles with a resin-forming material which will set to form a strong resin insoluble in water and oil on cont-act with a suitable catalyst and thereafter displacing the catalyst -down the well and outwardly from the well into the cavities 22 to cause the desired setting of the coating.

The substantially unitary permeable mass of particles 28 can also be obtained by displacing uncoated solid particles into the cavities 22 and then displacing a resinforming liquid down the well and through the mass of particles in the cavities 22 to coat the outer surfaces of the particles. The resin-forming liquid is followed by a liquid immiscible with the resin-forming liquid to displace that liquid, except for a coating on the particles, 4from the cavities 22. If the resin-forming liquid is one that will set at conditions of temperature and pressure existing in the cavities 22 to form a resin, pressure is maintained on the well until the resin-forming liquid sets to bond the particles together. If the resin-forming lliquid will set only on contact with a catalyst, the catalyst is suspended in a liquid and displaced through the cavities.

To maintain the desired permeability of the unitary mass of bonded particles, the particles should have a relatively narrow range of particle sizes such that the spaces between them are small enough to prevent ow of formation particles through the unitary mass of particles 28. Particles having a size in the range of 20 to 80 imesh, and preferably 40 to 60 mesh, are preferred. Fine particles such as particles having a size smaller than 100 mesh should be avoided. The solid particles should be generally granular in shape and resistant to deformation when subjected to uid pressure to prevent matting into a substantially impermeable mass. Suitable solid particles for use in this invention are granular particles o-f black walnut shells, peach pits, coke, sand, and the like. The particles, like the resin, should have a low solubility in the formation fluids and the 'liquid used to transport the particles into the cavities 22.

A preferred resin-forming liquid for bonding the particles together is a partially condensed mixture of phenol and lformaldehyde. Other resins suitable for bonding the particles are, for example, furfuryl alcohol resins,

urea-formaldehyde resins, epoxy resins, and alkyd resins. Details of bonding particles into a permeable mass are described in U.S. Patent No. 2,823,753 of Henderson et al.

It is an important advantage of this invention that the pressure in the well is maintained higher than the formation pressure during t-he drilling, cementing of casing, cutting of the cavity, displacement of the particles 28 into the cavity, and setting of the resin-forming coating on the particles. Thus, the incompetent formation is supported throughout the drilling and well completion to avoid movement of formation particles.

When an yabrasive slurry is used to cut a cavity to be packed with gravel, much of the formation that is damaged during drilling is removed from the well as the cavity is cut. Other methods of cutting notches such as gun or shaped charges do not remove the damaged formation.

The large diameter near the outer end of the cavities produced by the abrasive slurry has several advantages over the cavities produced by shaped charges used in perforating the casing. Because of the large size of the resultant unitary mass of bonded particles, the mass has substantial strength :and is not easily broken. It cannot be forced back through the perforations 20. Because of the large size of the cavity, the area of the incompetent formation in contact with the unitary mass of particles is large and the rate of flow of formation fluids from the face of the incompetent formation into the cavity is relatively low. Hence, the pressure drop and forces tending to break particles from the formation are relatively small. In contrast, the cavity produced by a shaped charge tapers outwardly and is relatively small. These factors encourage the displacement of the bonded particles back into the well and breaking of particles from the incompetent formation.

In contrast to bullet and jet perforations, the smallest portion of the hydraulic jet cut opening is in the casing and the largest portion is in the formation. The casing wall around the opening forms a strong bridge or support for the consolidated mass, and the consolidated mass is unsupported over only the narrow opening in the casing.

One of the advantages of this method is that the incompetent formation can be treated without the necessity of any reduction in the internal diameter of the well bore. Perforated liners or screens `are not required. Hence, upper zones of multiple completions can be treated according to this invention without interfering with subsequent operations at a lower level in the well.

I claim:

1. A method of controlling the movement of sand in a well having casing set through an incompetent formation comprising cutting an opening in the casing in the interval of the incompetent formation, discharging from a nozzle aligned with the opening and mounted on tubing extending down the well a high-velocity stream of an abrasive slurry outwardly through the opening to cut in the incompetent formation, a cavity having a width near its outer end substantially larger than the width of the opening in the casing, circulating the slurry and entrained particles cut from the formation during the cutting of the cavity upwardly through the well, displacing solid particles downwardly through the well and out into the cavity cut in the formation to fill the cavity, and bonding the particles to form a permeable coherent mass.

2. A method as set forth in claim 1 in which said particles have a resin-forming coating thereon, and the coating sets to form a resin while the particles are in the cavity.

3. A method as set forth in claim 1 in which said particles have a resin-forming coating thereon adapted to set at conditions of temperature and pressure in the incompetent formation, and the well is shut in until the coating sets to bond the particles into the permeable coherent mass.

4. A method as set forth in claim 1 in which said particles are granular and have a lcoating thereon settable to form a resin on contact with a catalyst, and the catalyst is displaced through the particle-lled cavity to cause setting of the resin-forming coating.

5. A method as set forth in claim 1 in which after filling the cavity with solid particles a resin-forming liquid is displaced down the well through the cavity to coat the particles with the resin-forming material, an inert liquid is displaced down the well and through the cavity to remove the resin-forming liquid from the spaces between the particles, and conditions in the cavity are maintained to cause formation of the resin to bond the particles.

6. A method as set forth in claim 1 in which the abrasive slurry is disch-arged from a nozzle supported within the casing to cut an opening in the casing, and the discharging of the abrasive slurry from the nozzle is continued to cut the cavity in the formation.

7. A method as set forth in claim 1 in which the nozzle is supported within the casing in the interval of the incompetent formation, the abrasive slurry is discharged from the nozzle, the nozzle is rotated about a vertical axis to cut a notch through the casing and extending completely around the casing, and the discharge of abrasive slurry and rotation of the nozzle is continued to cut a cavity extending 360 around the casing.

8. A method as set forth in claim 1 in which the particles have a size in the range of to 80 mesh.

9. A method of completing a well in an incompetent formation comprising drilling Ia borehole through the incompetent formation, setting casing through the incompetent formation, cutting an opening in the casing in the interval of the incompetent formation, discharging from a nozzle aligned with the opening and mounted on tubing extending down the well a high-velocity stream of an abrasive slurry outwardly through the opening to cut in the formation adjacent the opening a cavity having a width near its outer end substantially larger than the Width of the opening in the casing, circulating the slurry and entrained particles cut from the formation during the cutting of the cavity upwardly through the well, displacing a liquid having solid particles suspended therein downwardly through the well and into the cavity to fill the cavity, bonding the particles to form a permeable coherent mass supporting the walls of the cavity, and maintaining the pressure within the borehole of the well throughout the drilling, setting of casing, cutting of the cavity, cavity filling and bonding steps higher than the formation pressure.

References Cited UNITED STATES PATENTS 2,315,496 4/ 1943 Boynton 166-35 X 2,758,653 8/1956 Desbrow 166--222 X 2,823,753 2/1958 Henderson et al. 166-33 X 2,986,538 5/1961 Nesbitt et al. 166-12 X 2,990,016 6/1961 Goins et al. 166-2'9 3,175,613 3/1965 Hough et al. 166-35 3,209,826 10/1965 Young 166-33 3,255,819 6/1966 Scott et al. 166-21 3,327,783 6/1967 Ayers 166-33 3,336,980 8/1967 Rike 166-35 X OTHER REFERENCES Uren, Lester C., Petroleum Production Engineering: Oil Field Development, McGraw-Hill, ANew York, 4th ed., 1956, pp. 721 and 722.

CHARLES E. OCONNELL, Primary Examiner.

I. A. CALVERT, Assistant Examiner. 

